1. Field of the Invention
The present invention relates to a zoom lens, specifically to a zoom lens for electronic image capture apparatuses such as video cameras and digital cameras that achieve slim design in depth.
2. Description of Related Art
In recent years, as the next-generation cameras to replace silver halide 35 mm film (135 format) cameras, digital cameras (electronic cameras) have attracted a considerable attention. The digital cameras have come to contain many categories in a wide range from high-performance models for professional use to popular portable models. Under the circumstances, while slim design of a camera is one of important challenges, the thickness of an optical system, particularly that from the most object-side surface of a zoom lens to an image pickup surface has conventionally laid a greatest obstacle to reduction in depth of the camera. The recent major technique for slim design of a camera body is to employ a so-called collapsible lens barrel, which causes an optical system to protrude from the camera body in photographing while to be folded up into the camera body when carried. As an example of the optical system that could effectively contribute to thin design by employing the collapsible lens barrel, there is a type that includes a first unit having a negative refractive power and a second unit having a positive refractive power, which both are shifted in a magnification change (for example, refer to Japanese Patent Application Preliminary Publication (KOKAI) No. Hei 11-194274, Japanese Patent Application Preliminary Publication (KOKAI) No. Hei 11-287953, and Japanese Patent Application Preliminary Publication (KOKAI) No. 2000-9997).